docs: def pkdecrypt(self, conn):
          """Handle decryption using ECDH."""
          for msg in [b'S INQUIRE_MAXLEN 4096', b'INQUIRE CIPHERTEXT']:
              keyring.sendline(conn, msg)
  
          line = keyring.recvline(conn)
          assert keyring.recvline(conn) == b'END'
          remote_pubkey = parse_ecdh(line)
  
          identity = self.get_identity(keygrip=self.keygrip)
          ec_point = self.client.ecdh(identity=identity, pubkey=remote_pubkey)
          keyring.sendline(conn, b'D ' + _serialize_point(ec_point))